Known powder coating systems typically include a powder source, a powder pump, a powder spray gun, a hose connecting the pump to the gun and a pick-up tube that feeds powder from the powder source to the pump. Powder coating systems usually are designed to work with a plurality of colors of powder coating material. For many such systems, especially larger systems that use a plurality of guns to apply powder to larger objects, the powder coating material of the previous color must be removed from the system before the next color of powder coating material can be used. In larger systems this can involve a significant amount of down time to clean all the powder out of the system including having to purge powder residue from the pick-up tube, the pump, the hose and the gun. The faster the purging can be accomplished, the less is the overall down time required for a color changeover.
Various purging systems have been developed including those shown in U.S. Pat. Nos. 4,248,379 and 5,341,989, owned in common by the assignee of the present invention, the entire disclosures of which are fully incorporated herein by reference. However, to date no single system effectively purges and cleans the pick-up tube, pump, hose and gun in a single operation without substantial disassembly of the system and with minimum operator involvement.
It is desired, therefore, to provide new methods and apparatus for purging powder coating system components with reduced time and effort in order to speed up a color change operation.